5-Chloronaphthalene-2-carboxylic acid

100184-66-5

56961-89-8

Step (3) Preparation of 5-chloro-2-naphthalenecarboxylic acid: with reference to the method of W. Adcock et al. (Aust. J. Chem., 18, 1351 (1965)), NaNO2 (1.19 g, 0.0173 mol) was dissolved in a mixed solution of H2SO4 (15.6 mL) and HOAc (14.4 mL) at 10 °C [prepared by adding NaNO2 to cooled H2SO4, heated until dissolved, cooled again and added HOAc]. A suspension of 5-amino-2-naphthoic acid (2.70 g, 0.0144 mol) in HOAc (48 mL) was added to the above solution over 14 min. The resulting solution was slowly (within 15 min) added to a solution of CuCl (6.28 g, 0.0635 mol) in concentrated HCl (88 mL) preheated to 60°C. Heating of the reaction mixture was continued for 30 min. After cooling to 5 °C, it was diluted with H2O (200 mL) and filtered to obtain a gray solid (2.5 g). The solid was dissolved in hot EtOH, treated with activated charcoal and recrystallized to give a white solid product (1.15 g, 38%) with a melting point of 205 °C (literature values 263°-265 °C). NMR hydrogen spectrum (DMSO-d6, 400 MHz): δ 7.59 (dd, J = 7.5 Hz, 7.5 Hz, 1H), 7.83 (dd, J = 7.5 Hz, 1.0 Hz, 1H), 8.13 (dd, J = 8.7 Hz, 1.4 Hz, 1H), 8.15 (d, J = 8.7 Hz, 1H), 8.25 (d, J = 8.7 Hz, 1H), 8.68 (d, J = 1.4 Hz, 1H). Mass spectra: m/e 206 (100%), 189 (42%), 161 (42%).